title: Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface.
abstract: Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.
authors.affiliation: Max-Planck-Institut für Metallforschung, D-70569 Stuttgart, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Mezger
authors.forename: Heiko
authors.initials: H
authors.lastname: Schröder
authors.forename: Harald
authors.initials: H
authors.lastname: Reichert
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schramm
authors.forename: John S
authors.initials: JS
authors.lastname: Okasinski
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schöder
authors.forename: Veijo
authors.initials: V
authors.lastname: Honkimäki
authors.forename: Moshe
authors.initials: M
authors.lastname: Deutsch
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Ocko
authors.forename: John
authors.initials: J
authors.lastname: Ralston
authors.forename: Michael
authors.initials: M
authors.lastname: Rohwerder
authors.forename: Martin
authors.initials: M
authors.lastname: Stratmann
authors.forename: Helmut
authors.initials: H
authors.lastname: Dosch